1. Field of the Invention
The present invention relates to a method for folding over a plate, and particularly to a method which minimizes generation of harmful detritus.
2. Related Art
In the process of stamp-forming a plate, various methods for folding over a plate are used. A conventional method for folding over a plate is shown in FIGS. 4A-4C. A notch is dented into the plate at the place to be bent, as shown in step 11. The depth of the notch is approximately equal to half the thickness of the plate. Then the plate is bent 90 degrees at the notch, as shown in step 12. Finally, the plate is compressed until both portions thereof closely touch each other, as shown in step 13.
Another conventional method for folding over a plate is shown in FIGS. 5A-5D. A notch is dented in the plate at the place to be bent, as shown in step 11xe2x80x2. The plate is bent 90 degrees at the notch, as shown in step 12xe2x80x2. The plate is then bent a further 45 degrees, as shown in step 21. Finally, the plate is compressed until both portions thereof closely touch each other, as shown in step 13xe2x80x2.
Still another conventional method for folding over a plate is shown in FIGS. 6A-6C. A notch is dented in the plate at the place to be bent, as shown in step 11xe2x80x3. A comer of the portion to be folded over is chamfered. The plate has a thickness T. Half of the edge of the plate at which the comer is located remains straight, thus defining a distance T/2. The arc formed by the chamfer has a 1.0 millimeter radius. The plate is bent 90 degrees, as shown in step 12xe2x80x3. The plate is compressed until both portions thereof closely touch each other, as shown in step 13xe2x80x3. During such compression, the chamfer helps reduce friction between the plate and a rammer which punches the plate.
FIGS. 7A and 7B show a process of finally folding over a plate 50, in accordance with the conventional method illustrated in FIG. 4. The plate 50 is bent 90 degrees at a notch (not labeled) to form an upright foldedover portion 52. An L-shaped rammer 40 moves in direction C. The rammer 40 progressively rubs a side wall 522 of the foldedover portion 52, and thereby scrapes some hairlike chips and detritus 54 off of the side wall 522. Such chips and detritus 54 can change the size of the plate 50 and can reduce the quality of the plate 50.
Thus a method for folding over a plate which solves the above problems is desired.
Accordingly, an object of the present invention is to provide a method for folding over a plate which results in accurate sizing of the plate.
Another object of the present invention is to provide a method for folding over a plate which minimizes generation of detritus harmful to the plate.
To achieve the above-mentioned objects, a method of the present invention for folding over a plate comprises the steps of: providing a first mold assembly to dent a notch at the place of the plate to be bent and simultaneously form a curved portion at an end of the plate which has a rounded comer with a 1.0 millimeter radius; providing a second mold assembly to bend the plate 90 degrees at the notch; and providing a third mold assembly to finally fold over the plate with a rammer acting on the curved portion of the plate and thereupon flattening the curved portion.